The ternary Mn+1AXn, or MAX, phases (where M is an early transition metal, A is an A group element mostly groups 13 and 14, X is C and/or N, and n=1 to 3), phases are a large family, 70+, of nanolayered, machinable solids. There are approximately 50 M2AX, or 211, phases, five M3AX2, or 312, phases and a growing number of M4AX3, of 413 phases since that structure was first established in Ti3AlN4. In all cases, the Mn+1AXn unit cells are hexagonal—space group P63/mmc—with two formula units per unit cell. In these compounds, near close-packed M atoms are interleaved with a single layer of pure A-element; the X atoms occupy the octahedral sites in between the M atoms. In the 211's, every third layer is an A-group element, in the 312's every fourth layer, and in the 413's every fifth.
These MAX phase carbides and nitrides possess unusual and, sometimes, unique chemical, physical, electrical, and mechanical properties that combine the best attributes of metals and ceramics such as high temperature wear, corrosion resistance, and toughness. The MAX phases are electrically and thermally conductive due to their metallic-like nature of bonding. Most of the known MAX phases are better electric and thermal conductors than Ti. Because of these properties, MAX phase materials are useful in technologies involving high efficiency engines, damage-tolerant thermal systems, increasing fatigue resistance, and retention of rigidity at high temperatures. New applications based on reported superconducting behavior at low temperatures has spawned new interest in these materials.
Within this class of materials, the first and only Mo-containing MAX phase, Mo2GaC, was first synthesized in 1967 by reacting Mo and C powders with liquid Ga for four weeks at 850° C. in an evacuated quartz capsule. Superconducting behavior below 7 K has been reported. More recently a theoretical paper was published predicting some of its properties. Compared to Nb2GaC and V2GaC, Mo2GaC was predicted to have the highest bulk shear modulus and lowest shear modulus.
The present disclosure addresses the interest in MAX-phase materials in their own right and as precursors to MX-ene materials, generally, and the promise of such interesting properties for new Mo-containing materials, specifically.